1. Technical Field
This invention relates to ultrasonic detection systems and more particularly to an ultrasonic detector having a flat faced radiator.
2. Discussion
Ultrasonic detection systems have a wide variety of uses including object detection, range finding, level sensing, etc. In general, such systems include an ultrasonic transducer which is capable of transmitting, as well as receiving an ultrasonic beam. An ultrasonic transmitter and receiver unit may be used to transmit an electrical AC pulse at ultrasonic frequencies (15-100 KHz.) This electrical pulse causes the transducer to vibrate and thereby transmit a pulse of ultrasonic energy toward the object to be detected. When this pulse reaches the object, the pulse is reflected back to the transducer and the transducer produces an electrical pulse in response which is transmitted back to the transmitter and receiver unit. The time difference between the transmitted and received pulse, may be used to calculate the range of the object.
A number of problems arise in ultrasonic detection systems due to the spread of the ultrasonic wave before it reaches the desired object. This causes unwanted extraneous reflections back to the transducer from objects or surfaces other than the desired object. These extraneous reflections create noise in the received signal and may even completely mask the reflection from the desired object. In response, many ultrasonic detection systems include vibration absorbing damping systems in their mounting to prevent such direct transmission of ultrasonic energy. In response, many ultrasonic detection systems include a radiator for controlling the dispersion of the ultrasonic beam. For example, horn structures are frequently used to direct the path of the ultrasonic energy into a specific, defined direction. However, in a number of applications such protruding structures as horns are unacceptable because of their propensity to attract and trap debris and the difficulty in cleaning such protruding structures. For example, in ultrasonic level sensors used in sterilized environments, it is difficult or impossible to adequately clean a horn structure which is protruding into the sterilized cavity. Further, in many applications of ultrasonic detectors, space limitations preclude any protruding structure and a flat face must be used. An additional problem with prior ultrasonic detectors is that there may be a coupling of the ultrasonic energy directly from the transducer through the support structure to surrounding structures and surfaces which will also create unwanted received reflected signals. However, in many cases the isolating members add undesirable complexity, cost and bulk to the overall system.
Thus, it would be desirable to provide an ultrasonic detection system which transmits a well defined and easily controlled beam of ultrasonic energy in a single direction. It would also be desirable to provide such an ultrasonic detector which has a flat face and does not require any protruding horn or other structures to control the ultrasonic beam. Further, it would be desirable to have an ultrasonic detector which does not require complex isolating mechanisms to prevent direct production of ultrasonic energy into the surrounding mounting structure. Further, it would be desirable to provide an ultrasonic detection system with the above features which is relatively inexpensive to manufacture and simple to construct.